Lamp resistor



April 24, 1951 l.. soKoLoFF 2,550,169

LAMP RESISTOR Filed Dec. 29, 1948 2 Sheets-Sheet 1 .nuuunmulllll L. SOKOLOFF LAMP RESISTOR April 24, 1951 2 Sheets-Sheet 2 Filed Dec. 29, 1948 Patented Apr. 24, 1951 UNITED STATES PATENT OFFICE LAMP RESISTOR Louis soknlofr, chicago, 111. Application December 29, 1948, Serial No. 67,800

This invention relates generally to lamp rel sistors, and more particularly to lamp` resistors of the washer type which are insertable in a lampv socket to decrease the voltage applied to the lamp, thereby to increase lamp life.

It is frequently desirable to provide special lamps, for example, to mark exits and fire escapes, or to act as pilot lights, and the like, in which case the brilliance of the lamp or the electrical eciency thereof is not as important as is lamp life and the assurance of continued operation of the lamp over long periods of time, without requiring service or replacement. There are, of course, lamps of higher than normal voltage rating, which may be employed in sockets operating at normal voltage, to achieve long lamp life, but these lamps are extremely limited in available wattage ratings, and are not readily obtainable. Employment of a resistance in series with a standard or stock lamp, to decrease the voltage actually applied to the lamp, will have the effect of greatly increasing the life of the lamp, enabling more satisfactory performance in installations where long lamp life is a primary consideration.

An electrical resistor, of the type hereinbelow described, may be mounted in the same socket with a lamp, to afford the desired effect of greatly increasing lamp life. Such a resistor may be detachably secured by providing the samewith screw threads for engagement with the lamp socket threads, or it may be constructed so as to be loosely inserted in the socket vand maintained therein by the lamp, falling out when the lamp is removed.

In accordance with a specic embodiment of my invention, a resistor, connected in series with a lamp, to increase the normal life thereof, is provided with a thermally-responsive shunting element which automatically shunts out the resistance when the latter overheats due to an overload, thereby preventing damage to the lamp socket. Such overload may occur, for example, when a larger lamp is employed than originally contemplated. The shunting of the lamp resistor removes electrical load therefrom and allows the resistor to cool. The lamp itself remains energized at all times, operating, however, on full line voltage.

The washer resistor provided with thermal shunting means shunts out the resistance ele-l ment on an overload and continues to supply the lamp. This is a very important feature for particular installations as in the case of exit lights in public places, where it is desirable to 6 Claims. (Cl. 20L-49) have a constantly burning lamp. The shunting out of the resistance element allows it to cool.

While the thermalr shunting means is readily adaptable to a washer typevresistor, it can be used to advantages in various resistors, especially those of small size.

A thermal shunting element incorporated in a resistor constructed in accordance with my invention comprises one or more units constructed of fusible metal which are located adjacent the resistor. Upon overloading the resistor over a period of several minutes, the heat generated and accumulated in the resistor is sufficient to slowly melt the fusible'metal, causing the same to flow and establish a shunt across the terminals of the resistance.

In one preferred form of the invention, two fusible elements are utilized, one being connected to each terminal of the resistance. The fusible elements are so arranged with respect to one another, that upon application of suii-` cient heat to the elements over a sufficient period of time, one or both of the elements melt and the melted fusible metal runs together to form a continuous conductive path for electric current to shunt the resistance. After the fusible units have melted and run together they provide an alternative or shunt path for electric current flowing from the power line to the electric lamp. The resistor, being now effectively disconnected from Athe power line cools, thereby permitting the fusible metal to solidify and establish a relatively permanent path for current to the lamp. Accordingly, operation of the lamp is not interrupted upon overheat of the series resistance element, nor can the lamp socket be damaged by overheating of the resistance element.

The extent of overload, and the time duration of overload required to fuse the fusible metal in the resistance element of my invention is predetermined at the time the resistor is assembled by suitable choice of resistance value and by suitable choice of the size and composition of the fusible element.

It is, accordingly, a primary object of the present invention to provide a novel and improved lamp resistor for insertion in a lamp socket, which is extremely simple in construction, easy to install, inexpensive to manufacture and reliable and safe in operation.

It is another object of the invention to provide a novel resistance element provided with a. thermally responsive A shunting element therefor ,which operates toL shuntvthe. resistance under predetermined conditions of overload or overheating.

The novel features which I consider to be characteristic of my invention are set forth with particularity in the appended claims. The invention, itself, both as to its organization and its mode of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specic embodiment thereof, especially when read in connection with the accompanying drawings, where- Figure l is an elevational view, partly in vertical cross-section, illustrating a rosette type of fixture having disposed in the lamp socket thereof, a washer type electrical resistor constructed in accordance with the present invention.

Figure 2 is an enlarged vertical cross-sectional view taken through the lamp resistor.

Figure 3 is an enlarged plan view of a resistance wafer employed in the lamp resistor of Figure 2.

Figure 4 is an exploded view showing the main parts of the lamp resistor of Figure 2.

Figure 5 is a perspective view of a special device used in inserting the resistor in a lamp socket.

Figure 6 is an enlarged fragmentary sectional view showing a socket provided with a built-in resistor constructed in accordance with the principles of this invention.

Figure 7 is a diagrammatic view of the resistor circuit used in connection with the structure of Figure 6.

Figure 8 is a view similar to Figure '1 showing a modified form of resistor circuit.

Figure 9 is a view similar to Figure 8 showing still another form of resistor circuit.

While the resistor of the present invention may be employed in any conventional type of lamp socket, it is illustrated herein as employed in a lamp socket of a rosette type of fixture.

In the form shown, the washer type resistor unit, indicated generally by the reference character I0, is threadedly engaged interiorly of a shell II of the socket, within which is further threadedly engaged a lamp, indicated generally by the numeral I2. The shell I I is mounted within a usual insulating cup I3, secured within a lower portion I4 of a xture I5. The resistor unit I0 is positioned intermediate a center lamp contact I6 and a center socket contact I1, thus inserting the electrical resistance electrically between these two contacts, and consequently in series with the lamp filament.

The center contact I1 of the lamp socket is secured to the insulating cup I3 by a fastening screw I8, which also serves to secure a conductor I9 and to connect the same with the center contact I1. The shell I I is electrically connected to a conductor 20 by means of a fastening screw 2| in the usual manner.

The following detailed description of a specic embodiment of a washer type resistor unit I0, arranged and constructed in accordance with the present invention, will demonstrate that it may be used in any conventional type of lamp socket, and that its use is not restricted to the particular socket illustrated in Figure 1 of the drawings.

As illustrated in Figures 2 and 4 of the accompanying drawings, the reference numeral 22 designates a metallic shell or cup member formed with an inturned annular top ange 23. The interior wall of the shell 22 may be lined with suitable insulating tape 24, or with an insulating collar, as desired, to isolate the interior walls of the cup 22 from contact with the various metallic electrically charged elements contained therein. Inserted within the shell 22 in snugly-fitting relation, and bearing against the underside of the flange 23, is an insulating washer 25, having a circular aperture 26 centrally thereof. Located immediately below the insulating disc 25 is a metallic disc 21, which ts within the insulating tape or collar 24, and which is provided with a centrally located aperture 28. Located externally of the cup 22 and co-axially therewith, when assembled, and resting on the outer surface of the flange 23, is a further insulating disc 29 having a circular centrally located aperture 30.

A rivet 3I is provided, which may be passed through the apertures 28, 2B and 35, serving to secure these latter to the cup 22 by clamping the flange 23 between the insulating disc 29 on the outside of said flange 23, and the insulating disc 25 and the metallic disc 21 .located internally of the cup on the underside of the flange 23.

A further insulating washer 32 is provided, having a peripheral notch 33, the disc 32 being inserted in the cup 22 overlying the rivet 3I and the metallic disc 21.

Immediately beneath the insulating disc 32 is placed the resistance element, generally identined by the reference numeral 34, a specific mode of construction of which will be described hereinafter. Underlying the resistance element 34 is a further insulating disc 35 having a peripheral notch 3B, the disc 35 being identical in all respects with the disc 32, but the respective peripheral notches 33 and 35 being arranged in nonoverlapping relation when the unit is assembled for a purpose which will appear as the description proceeds.

Located beneath the insulating disc 35 is a further metallic disc 31, which may be identical with the metallic disc 21 and which, like the latter, is provided with a central circular aperture 38. Located beneath the metallic disc 31 is a further insulating Washer 39, which may be identical with the insulating washer 25, and which, like the latter, is provided with a central circular aperture 40. A rivet 4I, which extends through the apertures 38 and 4l), serves to clamp together the metallic disc 31 and the insulating disc 39, providing, however, an electrically conductive path between the disc 31 and the underside of the insulating disc 39.

For purposes of convenience the metallic discs 21 and 31 may be constructed to be of smaller diameter than the insulating discs 25, 32, 35 and 39, to assure that the metallic discs 21 and 31 will not come into contact with the metallic surface of the cup 22. This construction is not, however, essential since the insulating sleeve 24 is provided for the same purpose and would, in any event, prevent contact between the metallic discs 21 and 31 and the side of the cup 22.

In order to secure the insulating disc 32, the resistance element 34, the insulating disc 35, the metallic disc 31, and the insulating disc 39 firmly within the receptacle or cup 22 in the order recited, there is provided an annular member 42 having a thin wall 43 extending parallel to the axis of the annulus, and having an outwardly and radially extending flange 44 formed integrally with the upper edge of the annular ring 43. The annular flange 44 may be inserted within the cup 22, in contact with the insulating disc 39, and thereafter the lower-most edge 45 of the cup 22 may be bent inwardly under the underside of the flange 44.

There is thus formed a compact integral resistance unit, from which extend the rivets 3| and 4|, in opposite directions, said rivets 3| and 4| being in contact with the metallic discs 21 and 31, respectively, and being otherwise insulated from each other and from the metallic cup 22, insulating discs 25 and 29, which serve to clamp the metallic disc 2l to the ange 23 of the cup 22, and concentric insulating discs 32 and 35 which serve to isolate the resistance element 34, and by the insulating disc 39 which serves to isolate metallic disc 31, and consequently the rivet 4|, from the collar 42.

Referring now specifically to Figure 3 of the drawings, there is illustrated the resistance element 34, constructed in accordance with this invention, and comprising a flat, thin insulating Wafer 45, which may be fabricated of sheets of mica, or other suitable heat resisting material having the desired insulating properties, on which is wound a fine resistance wire 46, the length, thickness, and physical character of which may be so selected as to provide the required electrical resistance for insertion in series with the lamp |2 to accomplish the desired drop in line voltage, without establishing more than a predetermined relatively small amount of heat dissipation in the resistance unit. Formed integrally with the wafer 45 is a pair of projecting arms 41, 48, joined to the wafer 45 proper by neck portions 49 and 50 of relatively small dimensions, and separated from one another by a small U-shaped gap 5|. Secured about the neck portion 55 is a small collar 52 formed of fusible metal such as solder or lead having a relatively low melting point, and which is in electrical contact with and secured to one end 53 of the resistance wire 46. The remaining terminal 54 of the resistance wire 45, which is normally located remotely from the end 53, when the winding 45 is wound on the Wafer or form 45, is brought to a position adjacent the end 53 by stretching the end 55 of the wire 46 over a notch 55 at the remote end of the wafer 45, and then conveying the Wire, as at 51, between layers of mica, or the like, forming the wafer 45, so that the end portion 51 of the winding 46 is electrically insulated from the remainder of the winding 45, the terminal then being secured to a further collar or link fabricated of fusible metal and identified by the reference numeral 58. Y

The fusible collars or links 52 and 58 form the terminals of the resistance wire 46.

In assembling the resistance element 34 between the insulating discs 32 and 35, the peripheral notch 33 may be caused to over-lie the fusible collar 58 and the peripheral notch 36 to overlie the fusible collar 52, or vice-versa, as desired, so that the fusible collars 58 and 52 extend beyond the insulating discs 32 and 35, respectively, and into contact with the metallic discs 21 and 31, respectively. The collars 52 and 55 thus serve as terminals for the resistance wire 45.

Since the metallic disc 21 is secured bythe rivet 3|, the latter provides a means for conveying current to the terminal 58. On the other hand, since the metallic disc 31 is secured by the rivet 4|, which extends through the insulating disc 3S, the rivet 4| provides a means for conveying current to the contact or fusible element 52.

The assembled resistance element including v the fusible links may be inserted within the shell of a socket, the rivet 3| extending into the'contact with the central contact |1 of the lamp socket, and the central contact I6 of the lamp I2 extending into contact with the rivet 4|. The resistance element 34 is then connected in series with the lamp, and serves to reduce the voltage actually applied at the terminal of the lamp;

Should a lamp of higher wattage rating than contemplated ybe utilized in the fixture 5, the current flowing in the resistance wire 46 of the resistance element 34 will be greater than normal. For example, the current drawn by a 50 watt lamp is twice as great as the current drawn by a 25 watt lamp, so that the increase of current flow in the heating wire 46 when an oversized lamp is used in the fixture I5, may be very considerable, especially since heat loss in the resistance wire 46 is proportional to the square of the current flowing therein. Accordingly, after an over-size lamp has been burning in the fixture I5 for a period of several minutes, considerable heat accumulates adjacent to the resistance element 34, this heat being communicated to the fusible elements 52 and 58. After a short period these elements soften and melt, and finally flow, merging into one another and forming a single conductive path for the lamp current, this path being in shunt to the resistance element 46, substantially discontinues current flow therein, and in effect connects the lamp |2- directly across the power source I9, 20. The lamp I2 is thus not put out of service nor is the socket of xture |5 materially damaged, since the fusible elements 52 and 58 flow before the heat generated in the resistance element 46 can communicate itself to Vthe socket or the fixture.

The resistance unit I0 may be so constructed as to fit loosely within the lamp socket, and to be held within the lamp circuit by the pressure exerted by the base of the lamp I2. However, in accordance with a preferred form of the invention, the resistance unit may be retained within the shell of the lamp socket by threadedly engaging same with the lamp socket. For this purpose, there is provided an annular member 59 having an inwardly extending flange 60, which may be secured to the cup 22 by pressing the flange 6I! against the inwardly turned edge 45 of the cup 22, and thereafter bending the wall 43 of the annular member 42 under the flange 60, as shown at 6|, in Figure 2- of the drawings. The annular member 59 may be provided with threads 62, which are adapted to engage the internal threads provided in the socket In order to provide for ready insertion of the resistance element I0 within the socket a pair of inwardly directed protuberances 63 may be provided on diametrically opposite points of the vertical wall of the annular member 59. These protuberances 63 may be engaged by a special tool, illustrated in Figure 5 of the drawings, and which may preferably take the form of a flat, square or rectangular member 53, constructed of bre or the like, and having a width slightly less than the width of the internal diameter of the annular member 59 to enable ready insertion thereof into the annular member 59, and having likewise a sufficiently great width to enable engagement of the inwardly extending protuberances 63. The edges of the tool 64 may be engaged with opposite edges of the protuberances 63, to enable rotation of the annular member 55,

and thereby to enable threading of the annular member 59, :and consequently of the resistance element I6, internally of the socket member H.

Figure 6 shows a slightly modified form of the resistor element fusible shunting means embodying the principles of this invention. In this form such resistor element instead of being insertable into a socket is built as a permanent part of the socket.

In Figure 6 the reference numeral 65 discloses the usual metallic threaded shell of the socket, which shell is secured in any suitable manner to a base 66.

Secured to the outer side of the base 66 is an insulating housing 61 formed of molded plastic,

built-up mica or any suitable material. The housing 61 may conveniently be provided with an outwardly extending flange 68 which abuts against the outer face of the base 66 and through which rivets 69 and 1D may be engaged to secure said housing to said base. The rivet 16 alords a terminal for one conductor 1l of the electric circuit leading to a source of power supply and since the inner end of that rivet 10 is used to secure the shell 65 to the base, it is obvious that an electrical circuit is established between the conductor 1l and said shell. The base 66 is made of insulating material so that the various rivets or similar metallic members passing therethrough are insulated from each other.

The other side of the power line is designated by the reference numeral 12. This side of the power line terminates within the housing 61 being secured in position therein by a rivet or suitable member 13. rEhe resistor 1d mounted within the housing 61 serves the same purpose as the previously mentioned element 2.4i, but is a modified structure having one terminal connected at the terminal I-l and its other terminal connected to a rivet or suitable conductor `which extends through the base plate 5S for positioning and electrically in connection with a spring terminal 16 by which electrical contact with one side of a lamp mounted within the socket is established. From the spring terminal 16 current ows through the lamp iilament and thence to the shell 65 and conductor "el thereby completing the circuit.

The other side of the circuit is normally through the resistance element 14 but in the event that there is an overload or other condition causing L undue heating of the resistance element 14 beyond a predetermined amount, a mass of low melting point fusible metal 11 which is positioned at the end of the conductor 12 will melt and flow Vto the head of the rivet 15, thus shunting out the resistance element 14 and establishing a direct flow through the conductor 12, molten fusible metal, the rivet 'E5 and the spring terminal 16.

In Figure 1 there is shown a diagrammatic arrangement of the circuits of Figure 6.

In Figure 8 there is shown a modified arrangement wherein a mass of fusible metal 11a is also provided adjacent the head of the rivet 15 but separated from the mass of fusible metal 11. Upon overheating beyond a predetermined point due to overload or otherwise, both of the masses of fusible metal 11 and 11a will be reduced to molten condition and `will flow together, thus coupleting the shunting out of the resistor 14.

In Figure 9 a modied arrangement is shown wherein the mass of fusible metal, in this instance designated by the reference numeral 11b, is positioned on the base plate 66 between the end of the conductor 12 and the rivet 15. Upon melting due to overload or otherwise this mass of fusible metal 11b will establish a circuit between the rivet 15 and the end of the conductor 12 thus effectively shunting out the resistance element 14.

t will be apparent that in these modifications the same principle of operation exists as in the forms previously described, the modification of Figure 6 showing a construction wherein the resistance element and the fusible shunting means are permanently built into the socket when the same is manufactured.

While the principles of this invention have been exemplified in connection with a socket mounted resistor it will be apparent that these principles are applicable to all cases where it is desired to shunt out a resistor under predetermined overload or overheat conditions.

While specific embodiments of lamp resistors have been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

I claim as my invention:

l. In an overload protected washer type resistor for use in an electrical socket, comprising a wire resistance wound on a support member, in series electric connection with said socket, overload protection means in the form of a deposit of fusible metal secured by said support member adjacent to said wire resistance in a non-shunting position thereto, said wire resistance having little space for heat dissipation, and being constructed and arranged to heat up and fuse said deposit of fusible metal to shunting relation to said wire resistance upon an overload to said socket.

2. In a lamp socket, an overload protected resistance element comprising an insulated support member, a resistance wire wound on said support member and in series electric connection with said socket, overload protection means in the form of a deposit of fusible metal secured by said support member adjacent said resistance wire in non-shunting relation thereto, said resistance wire having little space for heat dissipation, and being constructed and arranged upon an overload to said socket to heat up and melt said deposit of fusible metal to shunting relation to said resistance wire.

3. In a lamp socket, an overload protected unit comprising a shell member litting within said socket, opposite terminals on said shell member for connecting a lamp to said socket in electric series relation, a wire wound resistor disposed within said shell and connected in series between said terminals, overload protection means in the form of a deposit of fusible metal on said resistor in non-shunting relation thereto, said resistor being constructed and arranged to heat up and fuse said deposit of fusible metal into shunting relation to said wire resistor, upon an application of an overload to said socket.

4. In a lamp socket, a shell member associated with said socket so as to connect a lamp mounted in said socket in series relation with said shell member, insulating elements disposed in said shell on opposite sides thereof, conductors carried by said insulating elements, an insulating support member disposed between said conductors, a wire resistance wound on said support member, said wire resistance being in series connection with said conductors, a deposit of fusible metal secured to said support member adjacent said wire resistance in non-shunting relation thereto, said wire resistance being constructed and arranged to heat up and melt said deposit of fusible metal into shunting relation to said Wire resistance, upon an overload thereto.

5. An article of manufacture, an overload protected resistor, comprising a unit having an insulated member, a resistance wire wound on said member, and having terminals for joining in series electrical relation, overload protection means in the form of fusible metal disposed on said resistor in non-shunting relation thereto, said resistance wire being constructed to heat up and melt said fusible metal into shunting relation to said Wire resistor upon an overload thereto.

6. An article of manufacture, an overload protected resistor, comprising a resistance Wire wound on a support member, and connected to terminals for series electrical connections, overload protection means in the form of fusible metal CES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,121,997 Gilson Dec. 22, 1914 1,126,369 Booth etal Jan. 26, 1915 1,221,232 Sherman Apr. 3, 1917 1,934,435 Lessmann Nov. '7, 1933 2,282,441 Whitlock May 12, 1942 

